Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!uunet!mcsun!hp4nl!phigate!ehviea!leo
From: leo@ehviea.ine.philips.nl (Leo de Wit)
Newsgroups: comp.sys.atari.st.tech
Subject: Re: Spurious interrupt
Message-ID: <885@ehviea.ine.philips.nl>
Date: 20 Aug 90 05:53:48 GMT
References: <883@ehviea.ine.philips.nl> <1166@uhnix2.uh.edu>
Reply-To: leo@ehviea.UUCP (Leo de Wit)
Organization: Philips I&E Eindhoven
Lines: 56

In article <1166@uhnix2.uh.edu> uace0@uhnix2.UUCP writes:
|Leo -
|
|Just as a guess, sounds like your interrupt is ocurring at the same time you
|are attempting to change it.  Just some observations:
|
|1) Be certain your interrupt is restoring any registers it destroys

Yep, it is _very_ simple (also in order to have a fast counter):

myint
    add.l  #1,counter
    rte

|2) Be certain _not_ to save registers onto the stack, but rather use a static
|   storage area

Does not apply here.

|3) If neither one of those help, try masking off interrupts by raising your
|   ipl to 7 before issuing the xbtimer() call.  From what I can see of the
|   xbtimer() call, it does not touch the ipl when it is initing the mfp, so
|   you can conceivably be interrupting when you are changing.  Altho, the
|   xbtimer() call does disable the interrupt before changing it...

Ah, but the spurious interrupt does indicate problems with the MFP, not
with the 68000; if I understand correctly, it generally indicates that a
BUSERR occured on a periferal chip. So masking all interrupts shouldn't
help (but it won't hurt to give it a try).

In your second note:

|Also, 24 bombs is not real.  Chances are you are getting 2 or 3 bombs (address
|error (3 bombs) or BUSSERR bus error (2 bombs)) but repeatedly.  In other words,
|the system crashes, attempts recovery, crashes again, etc. until it locks up.
|
|Well, 24 bombs is real, but I've never seen it occur...

But it is most definitely exception 24 (spurious interrupt); this is
not only indicated by the ST bomb thrower - which occasionally is
unreliable - but also the exception save area indicates this. And
catching vector 24 and retrying does solve the problem ...

B.T.W. thanks for your suggestions, Mike. If someone is still
interested, I'll try to cut out a minimal code fragment to hack on.

|
|- mike
|
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    Leo.